STRUCTURE OF THE NEPHEIDIA OF DIKOPHILL'S. odd 



one another. As the preparation gradually dies they are the 

 first to stop^ while their flagella in the nephridial canal still 

 continue to make a few sluggish movements. Under com- 

 pression they seldom remain active longer than fifteen minutes, 

 at the end of which time their action has become quite slow. 

 They never show any tendency to unite together for mutual 

 support in the body-cavity as in some PolychaBts, but always 

 remain separate. Their protoplasm is clear and remarkably 

 free fi-om granules, and is, for this reason, highly refractive. 

 As already mentioned, the solenocytes of the first nephridium 

 seem somewhat finer than those of the following segments, 

 and in several cases their ends appear as if slightly flattened 

 and hook-shaped ; these are smooth, and never throw off pro- 

 toplasmic processes into the body-cavity as in Polygordius. 

 There is also considerable variation in size between those 

 attached to the margin and those attached to the centre of 

 the end of the nephridial canal, the latter being much longer 

 and more decidedly pear-shaped in form ; their long stems 

 densely packed together afford considerable support to the 

 mass of solenocytes. Beyond the refractive granule men- 

 tioned (figs. 2 and 5) as sometimes distinguishable in their 

 heads, no obvious evidence of the presence of a nucleus is 

 visible in the living state, nor in the second portion of the 

 nephridium, the thick granular-walled part, could I ever dis- 

 tinguish the presence of nuclei. It will be seen from Meyer's 

 (16) figure of one of the nephridial canals of D. gyrociliatus 

 (fig. 10) that a conspicuous nucleus is present on one side of 

 the canal. I have never observed any such nucleus in 

 D. tfeniatus. 



I have never seen excretory matter passing down the 

 nephridial canals in the form of granules, and they would 

 seem to excrete clear watery fluid alone. Whatever function 

 the so-called body-cavity performs, it is certain that the light 

 orange fluid filling it mast at least play a considerable role 

 in the areation and the removal of waste products from the 

 body tissues among which it ramifies. In the removal of 

 this fluid by osmosis the solenocytes, with their hyaline tubes, 



VOL. 50, PART 4. NEW SERIES. 39 



